A method for forming an inkjet image can form an image easily and inexpensively, being thereby utilized in a wide variety of printing fields such as photography, various prints, signs, or color filters.
Over recent years, demand for signs printed on a non-water absorptive recording medium such as vinyl chloride by using a aqueous ink having low environmental load have increased for various applications such as an outdoor signboard which requires long term weather resistance or a printed matter which requires adhesion to an object having a curved surface. However, it was difficult for the aqueous ink to obtain sufficient abrasion resistance on non-absorptive recording medium, and it needs to improve abrasion resistance. In order to improve the abrasion resistance on non-absorptive medium such as vinyl chloride, disclosed are the aqueous ink which contains resin and a cross-linking agent (for example, refer to Patent Document 1). However, even though the abrasion resistance is improved, since a cross linking reaction after ejection of the aqueous ink is rate limiting, it requires much time to cure a resin with a cross-linking agent in this technology. Therefore, the improvement in a cross linking reaction rate was an issue. Even though a mean in which a medium is heated at high temperature is known in order to accelerate the cross linking reaction rate, it can apply only to a medium having a heat-resistance, and there is a problem which causes loosing media flexibility.
Further, applications to high-speed printing to non-absorptive media (such as vinyl chloride, art paper, or coated paper) have been expanding. However, when an image is formed on such a medium using aqueous inks, there has been produced such a problem that spotting and bleed (hereinafter referred to as bleeding) occur due to aggregation among inks. To improve this image quality degradation, it is known that ink viscosity needs to increase to some extent immediately after printing. As a technology to increasing viscosity, disclosed was a technology in which an inkjet ink containing a non-water soluble resin neutralized with an amine as a binder resin is used, whereby bleed is considered to be reduced (for example, Patent Document 2). However, this technology could not result in satisfactorily resolving the problem of the bleeding.